Great Plains NTA3007HD Operator Manual - Manual (Page 84)

80 NTA907HD or NTA3007HD
166-207M 04/04/2011
11. Turn the calibration crank for the number of turns to
simulate
1 ⁄
10
hectare (or
1 ⁄
10
acre).
Note: It is important to turn the calibration crank rapidly.
Use a comfortable speed not exceeding
2 revolutions per second, which would simulate
10 kph (6.2 mph) planting speed. A longer calibra-
tion is always more accurate, especially for low
rates and small seeds.
1 ⁄
10
hectare is easy to calcu-
late and is a minimum calibration run.
See table at right for revolutions per area.
12. Wipe all the material off the flanges around the
meter doors and capture that material in the calibra-
tion container.
13. Accurately weigh the container plus material.
14. Subtract the empty container weight to determine
the application rate for
1 ⁄
10
acre (or
1 ⁄
10
hectare).
15. Press the Stop softkey on the monitor
and enter the sample net weight (SampleWeight).
The monitor responds with a Calibration Constant.
Push the Save softkey to accept this
value.
16. Multiply the sample size by 10 to determine applica-
tion rate per acre (hectare) at the current variable
rate gearbox setting.
If the calibrated rate matches the target rate, skip to
step 22. Otherwise…
17. Subtract the calibrated rate per acre (or hectare)
from the target rate to determine a rate correction
difference.
18. Determine a new chart rate, based on the previous
chart (not target) rate. To lower for the next rate:
To raise for the next rate:
Calibration Crank Revolutions
NTA907HD
Revs/hectare 1050
Per 1/10th ha 105
NTA3007HD
Revs/acre 425
Per 1/10th ac 42.5
Example:
MeasuredWeight is 23.3 kg
for container plus sample
ContainerWeight is 1.52 kg
SampleWeight = 23.3 - 1.5, which is:
21.7 kg
SampleWeight MeasuredWeight ContainerWeight – =
Example:
CalibratedRate = 21.7 x 10, which is:
217 kg/ha
This is 8% higher than our target rate of 200 kg/ha.
However, because the gearbox actuator effect is not lin-
ear, we cannot simply adjust it 8%.
CalibratedRate SampleWeight 10 × =
Example: TargetRate = 200
RateDifference = 217 - 200,
which is: 17 kg
The calibration run metered 17 kg too much.
You must lower the gearbox setting to compensate.
RateDifference T etR arg ate CalibratedRate – =
Example: Need to lower
RateDifference = 17 kg
OldChart = 201.3
NewChart = 201.3 - 17, which is:
183.9
nearest chart value is: 183.5
NewChart OldChart RateDifference – =
NewChart OldChart RateDifference + =